Abstract
Makovac & Gerbino (2009 a, b) reported increases of the multisensory response enhancement (MRE) when audiovisual AV components of a cross-modal event are (a) formally congruent, like in the takete-maluma phenomenon, and (b) in close spatiotemporal proximity, a necessary condition for multisensory integration by the superior colliculus and other brain areas (Calvert et al. 2000). While previous studies required observers to explicitly evaluate target properties, our MRE effects were obtained by asking observers to detect the occurrence of V targets and to ignore sounds, in either A and AV trials. Data were consistent with general principles of multisensory integration (spatial rule, temporal rule, inverse effectiveness rule).
In the present research we utilized a combination of implicit tasks to study three aspects of MRE effects: (1) the interaction between the structural components of cross-modal stimulation, formal congruency and spatiotemporal proximity; (2) the optimal AV asynchrony compatible with low-efficiency stimuli; (3) the relationship between superadditivity and automatic activation as criteria for defining multisensory integration. Formal congruency was manipulated by varying the degree of similarity between the sound intensity profile and the 2D visual shape of short (<100 ms) AV events. The optimal (i.e., inducing a maximum MRE) stimulus onset asynchrony was compared to perceived simultaneity of AV stimuli for each observer, measured in a control condition. Superadditivity was evaluated by comparing the estimates of top performances in unisensory and multisensory sessions. We discuss our results in the context of current psychophysical and fMRI evidence on formal (Gallace & Spence 2006), semantic (Hein et al. 2007), and training-induced (Naumer et al. 2008) congruency effects in AV object representation.
MS01_00006 grant (Industry 2015).